In microwave communications systems and other wireless communications systems, a RF converter is used for frequency translation and power amplification of transmitted and received RF signals. When a RF signal is transmitted by a radio transceiver, a control signal is sent from the transceiver to the RF converter. Upon reception of the control signal, the RF converter switches to the transmit mode, i.e., it supplies direct current (DC) power to its transmit amplifiers and disable its amplifiers in the receive chain. The RF converter also performs frequency up-conversion, i.e., it translates the RF signal from the signal intermediate frequency band to an assigned transmit frequency band before sending the RF signal to an antenna for transmission. Upon termination of the control signal from the transceiver, the RF converter switches back to the receive mode, i.e., it supplies direct current (DC) power to its receive amplifiers and disable its amplifiers in the transmit chain. When a RF signal is received via the antenna, the RF converter amplifies and down-converts the RF signal from the receive frequency band to an intermediate frequency band for further processing by the transceiver.
The antenna is usually connected to the RF transceiver by a coaxial cable. It is desirable to locate the RF converter near the antenna in order to reduce noise in the received RF signals, and to minimize transmitted signal power loss in the coaxial cable.
However, by placing the RF converter atop an antenna tower, remotely from the base station radio unit, the RF converter does not have access to the radio unit control signals, unless it is connected to the base station radio unit by a wire, in addition to the coaxial cable. Wire connection would cause other problems to the system. Thus, the RF converter, if located remotely from the base station radio unit, must be able to generate its own control signals. There is presently a need for a circuit which, when implemented as an integral part of the RF converter, allows the RF converter to sense when the base station radio unit is transmitting and to generate its own control signals so that it can switch between the transmit and receive modes in unison with the base station radio unit.